Barrel-type batch gas carburizing furnace

ABSTRACT

A ROTARY BARREL-TYPE RETORT IS POSITIVELY DRIVEN, ALONG WITH A PAIR OF ELONGATED SUPPORTING ROLLERS CRADLING THE SAME, BY DRIVE MEANS DISPOSED IN THE ENTIRETY THEREOF EXTERNALLY OF A CYLINDRICAL FURNACE HEATING CHAMBER IN WHICH THE RETORT IS CONCENTRICALLY LOCATED FOR ROTATION. PART LOADING AND UNLOADING CHUTE COMPONENTS ARE AT THE SAME AXIAL END OF THE HEATING CHAMBER, WITH THE RETORT BEING ROTATIVELY SUPPORTED IN PART, IN SUPPLEMENTATION OF ITS CRADLING SUPPORT ROLLERS, BY A TRUNNION AT THE OPPOSITE AXIAL END OF THE HEATING CHAMBER. MEANS FOR ROTATING THE RETORT ARE ASSOCIATED WITH THE TRUNNION, IN COMMON WITH MEANS FOR ROTATING THE RETORT-SUPPORTING ROLLERS, AND IN EACH CASE THE RETORT AND ROLLER DRIVE MEANS ARE ENTIRELY EXTERNAL OF THE HOT HEATING CHAMBER. IN ONE EMBODIMENT OF THE FURNACE DIRECT FIRING GAS BURNERS DISCHARGE PRODUCTS OF COMBUSTION INTO THE HEATING CHAMBER IN A DIRECTION GENERALLY TANGENTIAL OF THE RETORT. IN ANOTHER EMBODIMENT, U-TYPE RADIANT HEATERS ARE EM-   PLOYED. ATMOSPHERE GAS IS INTRODUCED TO THE RETORT VIA AN INLET PASSAGE IN THE RETORT JOURNALLING TRUNNION, EMERGING AT THE OTHER RETORT END AND FLOWING INTO THE COMBUSTION CHAMBER THEN OUT THE FURNACE FLUES. A GAS INLET IS ALSO CONTEMPLATED IN THE PART LOADING CHUTE AT A HEATING CHAMBER END, SUPPLEMENTING THE SUPPLY OF ATMOSPHERE GAS THROUGH THE RETORT TRUNNION.

5 Sheets-Sheet 1 wpi UM N Sept. 20, 1971 E. c. BAYER BARREL-TYPE BATCH GAS CARBURIZING FURNACE Filed Oct. 20', 1969 INVENTOR ATTORNEYS a ll) v 1 v 1 1 p H/ v I Ir 17 p 0; 1 E. c. BAYER 3,606,285

BARREL-TYPE BATCH GAS CARBURIZING FURNACE Filed Oct. 20, 1969 5 Sheets-Sheet 2 I N V E N TO R [OfI APD c. 5A 5/ r v- ATTORNEYS Sept. 20, 1971 E. c. BAYER 3,506,285

BARREL-TYPE BATCH GAS CARBURIZING FURNACE Filed Oct. 20, 1969 5 Sheets-Sheet 3 INVENTOR [0W4A0 C 514)? ATTORNEYS Sep 2 71 E. BAYER 3,606,285

I BARREL-TYPE BATCH GAS CARBURIZING FURNACE Filed Oct. 20, 1969 5 Sheets-Sheet 5 INVENTOR [DH/4RD C 514K634 ATTOR NEYS United States Patent 3,606,285 BARREL-TYPE BATCH GAS CARBURIZIN G FURNACE Edward C. Bayer, Dearborn, Mich., assignor to Holcroft & Company, Livonia, Mich. Filed Oct. 20, 1969, Ser. No. 867,460 Int. Cl. F27b 7/08 U.S. Cl. 263-34 19 Claims ABSTRACT OF THE DISCLOSURE A rotary barrel-type reto-rt is positively driven, along with a pair of elongated supporting rollers cradling the same, by drive means disposed in the entirety thereof externally of a cylindrical furnace heating chamber in which the retort is concentrically located for rotation. Part loading and unloading chute components are at the same axial end of the heating chamber, with the retort being rotatively supported in part, in supplementation of its cradling support rollers, by a trunnion at the opposite axial end of the heating chamber. Means for rotating the retort are associated with the trunn1on, 1n common with means for rotating the retort-supporting rollers; and in each case the retort and roller drive means are entirely external of the hot heating chamber. In one embodiment of the furnace direct firing gas burners discharge products of combustion into the heating chamber in a direction generally tangential of the retort. In another embodiment, U-type radiant heaters are em.- ployed. Atmosphere gas is introduced to the retort via an inlet passage in the retort journalling trunnion, emerging at the other retort end and flowing into the combustion chamber then out the furnace flues. A gas inlet is also contemplated in the part loading chute at a heating chamber end, supplementing the supply of atmosphere gas through the retort trunnion.

BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to the field of mass batch treatment of parts, for example gas carburizing, and more particularly, to apparatus of the barrel-type, into a rotatively driven retort of which the parts are charged and from which they are dumped after treatment, the retort being intensely heated in a sealed heating chamber in which it rotates coaxially. Specifically, gas carburizing is contemplated in an operation in which atmosphere gas is introduced into the retort during a cycle of treatment, the heating chamber and retort being tilted in a vertical plane including the retorts rotative axis to discharge the treated parts, as to a quench tank.

(2) Description of the prior art The most pertinent prior art of which I am aware is represented by Holcroft Letters Patent No. 3,318,591 of May 9, 196-7, the present invention relating to significant improvements of various sorts on that equipment, to be described.

SUMMARY OF THE INVENTION The invention affords an improved rotary barrel or retort-type gas atmosphere furnace well suited for the mass heat treatment of relatively small parts. Pursuant to the invention a fixed cylindrical and substantially gas tight, thermally Well insulated heating chamber is pivotally mounted by trunnion means on a pedestal-type base, and improved fluid cylinder means are provided for a tilting change of the chambers inclination on the trunnion axis during the treating operation. A partsreceiving, heating and treating retort is supported for powered rotation about an axis coaxial with that of the chamber, and the retort discharges upon being tilted downwardly, at the conclusion of the treatment, through unloading chute means at one end wall of the heating chamber. Pursuant to another improvement of the invention the retort is charged with parts or pieces to be treated at the same end wall of the chamber, which leaves the opposite end wall of the heating chamber available for the reception of hollow retort trunnion or journalling means acting in conjunction with roller supports on which the retort rests, these supports being similar to those shown in my patent.

Furthermore, both the retort trunnion and the supporting rollers are positively driven by chain-sprocket and gear type means disposed completely externally of the hot heating chamber and not subject to deterioration in the latters gaseous atmosphere, rather than involving rotary rack-type retort drive means within the chamber, as in the case of the furnace of the patent identified above.

As a further advantage related to the journalling of the retort trunnion in the heating chamber end wall opposite the loading and unloading wall, the hollow trunnion affords access to the retort interior for tubular means for the introduction of atmosphere gas into the retort. In further accordance with the invention, this gas emerges from the retort adjacent the opposite, loading and unloading end of the heating chamber, thence out the furnace flue. Deposition of carbon on the retortsupporting rollers is prevented, in turn minimizing a tendency to slippage of the retort on the rollers.

It is also contemplated that a slight counterfiow of atmosphere gas will be set up at the loading-unloading chute end of the combustion and/or heating chamber to assist in preventing the infiltration into the retort of combustion products from the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view, in general, in vertical axial cross-section through a carburizing furnace in accordance with one embodiment of the invention, characterized in common with the other embodiment in that article charging and discharging stations are located at the same axial end of the heating chamber of the furnace, the view also showing improved fluid pressurized cylinder means for tilting the furnace chamber from a solid line to a dotted line position;

FIG. 2 is a view in transverse vertical section on line 22 of FIG. 1;

FIG. 3 is a highly schematic perspective view illustrating an improved external chain-sprocket and gear arrangement for driving the retort and its supporting rollers; 7

FIG. 4 is a view in axial cross-section, similar to FIG. 1, of a second embodiment of the invention, in which the furnace heating chamber is equipped with tangentially firing gas burners, a. showing of other provisions, including means for tilting the heating chamber, being only very schematically shown in the interest'of simplicity; and

FIG. 5 is a view in transverse vertical section on line 55 of FIG. 4.

DESCRIPTION OF PREFERRED EMBODIMENTS A first embodiment 10 of the improved carburizing furnace of the invention is illustrated schematically in FIGS. 1 and 2, with its rotative drive arrangement being even more plainly shown -in perspective in 'FIG. 3. This drive is common to the furnace 10 and the other furnace embodiment appearing in FIGS. 4 and 5. Both of these incoporate structural provisions which, insofar'a's tlie Patented Sept. 20, 1971 composition of the furnace heating chamber, its rotary retort, the latters roller supports, etc., are quite similar to corresponding components shown and described in my Letters Patent No. 3,318,591 identified above; and in connection with the heating 'chambers radiant heaters, per FIGS. 1 and 2, the patent shows a very similar arrangement. Accordingly, in the interest of clarity and simplicity basic component features which are more fully illustrated and described in the patent will be but briefly referred to herein, the description being supplemented from time to time, nexus-wise, by reference to the patent.

The furnace embodiment 10, like that of the patent, comprises a cylindrical heating chamber 11 made up of an external sheet metal casing 12 backed directly about its periphery and at one end wall 13 by layers of appropriate insulation material 14 with the insulation in turn backed by fire brick 15. The opposite axial end wall 16 of the heating chamber 11 is of fire brick telescoped within that chamber end; the wall 16 receives various structurally improved components to which certain aspects of the present application relate, as will be described.

'FIG. 1 shows in solid line the normal horizontal operating condition of the furnace, generally designated .10, and, in dotted line, its position as tilted to discharge the treated parts, which change of inclination is accomplished in the furnace of my patent designated above by electric motor, chain and sprocket means. Pursuant to one of the present improvements, this tilting change of inclination, and return to normal position, is now accomplished in both of the embodiments shown herein through the agency of considerably simpler, yet equally effective fluid power means.

-As depicted in FIGS. 1 and 2, such means comprises an appropriate hydraulic cylinder 18 pivotally connected at 19 to a suitable fixed base support bracket 20, the upwardly extending plunger 21 of this cylinder being pivoted to bracket means 22 fixedly depending from the cylindrical furnace wall. The furnace is medially journalled for tilting in a vertical plane including its axis by means as shown in my patent. Cylinder 18 may typically have a four-inch bore and a fifty-inch stroke, being a double acting unit for a positive operation in reversely changing the axial inclination of heating chamber 11, and to this end having pressure lines 23, 24 in communication with its respective capped ends. The control of the pressurization of the cylinder through these lines may be selectively effected through suitable timing means serving to reversibly control theaction of appropriate valve means, not shown and not germane to the present invention, but of a type susceptible of automatic control consistent with continuous mass output operation. As in the case of the patented furnace, the present heating chamber 11 is pivotally mounted by diametral trunnions 26 midway of its axial ends on massive side floor pedestals 27, these constituting a part of a base for the furnace structure.

The rotary barrel-type retort 28 of furnace is mounted, pursuant to the present improvement, in quite a different manner than the corresponding retort of my patent, in view of the fact that the part loading and unloading provisions, hereinafter described, are located at a single axial end wall of the furnace, i.e., the right hand wall 13 as viewed in FIG. 1. Thus, the opposite or left hand end wall 29 of retort 28 is schematically shown as being axially provided with an elongated hollow cylindrical trunnion member 30, appropriately joined gas-tight in any desired fashion to the remainder of the chamber, which trunnion extends through the fire brick end wall 16, projecting a substantial distance outwardly thereof to receive retort drive means to be described. Tubular trunnion 30 at the same time affords access space receiving an externally supplied atmosphere gas tube 31 discharging to the interior of the retort at its axial midpoint, the tube 31 extending inwardly through an otherwise closed and sealed end wall 32 of trunnion 30.

Retort 28- is internally ribbed longitudinally at 33 in the manner of the Holcroft patent.

The rotatively stable support provided for retort 28 by the elongated trunnion is supplemented by elongated supporting rollers 34, located beneath and on either transverse side of the retort axis (the schematic showing of FIG. 1 being of course distorted in relation to the position of a supporting roller 34). tRollers 3'4, 35 are rotatably journalled appropriately in the opposite axial heating chamber walls 13, 16, as by sealed collar or bushing means '36 (FIG. 1); and reduced diameter stem extensions 37, 38 at one end of the respective rollers 34, 35 receive drive from a chain-sprocket and gear type arrangement or assembly schematically depicted in FIG. 3. This assembly effects a positive rotation of the retort cradling rollers 34, 35, as well as of the axially outwardly projecting, tubular retort trunnion 30, the retort 28 being thus rotated uniformly regardless. of any possible tendency to slip at the rollers.

With special reference to schematic FIG. 3, the drive extension 38 of the retort supporting roller 35 is shown as being longer than the corresponding extension 37 of roller 34; and it has a sprocket 39 fixed thereon adjacent its outer end. This sprocket is driven by a chain 40 from a motor-reducer unit generally designated by the reference numeral 41. Appropriate outboard bearings 42 (FIG. 1) journal the roller shaft extensions 37, 38 outwardly of the bushings 36.

In all cases, the chain and sprocket provisions, as described above and later, may of course be replaced by equivalent belt and pulley or like drive means, being immune to deteriorative heating chamber eifects. The same is true as to equivalency in regard to certain gear means to be described.

Adjacent the heating chamber 11, but still external thereof, the roller drive extension 38 has another sprocket 43 fixed thereon; and a power transmission chain 44 is trained about sprocket 43 and a sprocket 45 of the same diameter which is fixed on the drive extension 37 for the other supporting roller 34.

At a point axially intermediate the sprockets 39-, 43 the roller extension 38 fixedly carries a third output sprocket 46, which connects by a transmission chain 47 with a sprocket 48 secured on a jack shaft 49. This shaft is appropriately journalled to rotate in the axial end wall 16 of heating chamber 11; and it carries a drive gear 50 externally of the chamber. Gear 50 meshes with a similar gear 51 fixed on a shaft 52 which is journalled, as by an appropriate bushing similar to the bushing 36 journalling shaft 38, in the end wall of heating chamber 11. Just outwardly of the bushing 36 of shaft 52, the latter fixedly carries a drive sprocket 5 3, which is connected by a chain 54 with a somewhat larger diameter sprocket 55 fixed to the retort journalling extension 30, the sprocket 55 being in the vertical plane of its driver 53 and external .of the chamber wall.

The above-described external gear and chain-sprocket drive assembly of FIG. 3, generally designated 56, is shown in FIG. 1 as having its components which are located directly adjacent chamber wall 16 housed in a casing 57 which may be ventilated.

It is at the heating chamber end wall 13 opposite the wall 16 that a fixed discharge chute 58 of the furnace is connected, in the manner of Pat. No. 3,318,591. It is at this same wall :13 that the main, downwardly extending part loading or charging chute 60 is mounted (in structure similar to the patent), the chute 60 being serviced by an auxiliary charge tube 61 insertable in its open end. Chute 61 is pivotally connected by a parallel arm linkage 62 to a bracket externally fixed on the end wall and, as operated by fluid motor, rack and gear or equivalent means (not shown but, such as are disclosed in my patent), the auxiliary chute 61 is movable from an operative position, shown in solid line in FIG. 1, to a retracted position ap- I pearing in dot-dash line, and vice versa. Also as shown in the patent, the main chute 60 will be closed by an appropriate door when chute 61 is retracted.

Pursuant to the present invention the chute 60 is provided with an upright fitting 63 which is adapted to be connected to the source of atmosphere gas, for example, a combination of carrier or generator and .hydrocarbon components in the case of carburization, which source also supplies the atmosphere gas tube 31 at the opposite end wall 16 of the heating chamber. The gas thus fed to the interior of retort 28 emerges from the latter to the heating or combustion chamber at a slight annular clearance between the right-hand end (FIG. 1) of the retort and the receiving end of discharge chute 58, the gas being then disposed of suitably through vent or flue provisions of the furnace. The secondary gas inlet at 63 tends to prevent infiltration into chute 60 of products of combustion from chamber 11.

U-type radiant gas or oil heated tubes 65, 66 and 67 are fixedly sustained within the heating chamber in any appropriate manner, for example, by side brackets 68 and hanger means 69, these tubes extending through refractory packings 70 in the end wall 16 of chamber 11. They are supplied at one leg thereof by air and combustible lines (not shown) and discharge through the opposite leg to the furnace flue. However, open firing of the chamber interior is also contemplated, i.e., direct firing.

Vent tubes 71 extend in opposite directions from a level adjacent the bottom of chamber 111; these connect to the furnace flue system to dispose of the combination of combusted gaseous products. The discharge through the vent tubes 71 includes the combustion product of the tangentially fired combustion medium and the spent atmosphere gas.

FIGS. 4 and 5 illustrate another embodiment 72 of the improved furnace featuring such firing, which embodiment is very similar to the embodiment in many respects, including the dual atmosphere gas supply, the fluid cylinder provisions for tilting the heating chamber, etc. In the interest of simplicity, therefore, such tilting means has been only line-shown in FIG. 4. Other provisions which correspond to means illustrated in FIGS. 1, 2 and 3 are designated by corresponding reference numerals, primed.

Thus, the retort 28' has a reduced diameter hollow cylindrical trunnion 30 secured thereto and journalled in the furnace wall 16, a hole 73 in the retort end 29' placing the retort in communication with the trunnion interior. An atmosphere gas inlet tube 31' discharges into the interior of the trunnion member 30', which has a rotating journal in wall 16'.

The drive of trunnion 30 and barrel 28 is through a chain-sprocket and gear system like that denoted 56 in FIG. 3. That is, it includes a sprocket 55' secured on the trunnion, and the drive of the elongated extension 37 of the retort supporting roller 34' is through the agency of a sprocket 45' on the roller extension, the latter having an outboard journal at 42. For other parts of drive assembly 56' see FIG. 3.

In the embodiment 72 of FIGS. 4 and 5, direct or open firing as burners 75 are mounted in the cylindrical wall of the furnace, being disposed (FIG. 5) to fire substantially tangentially of the retort 28. They are staggered longitudinally on opposite sides of the furnace wall, the burning gas wrapping circumferentially about retort 28 to produce a very intense but uniformly distributed heating of the retort interior.

The furnace adaptations 10 and 72 afford, in a most simple, efficient and structurally practical way, environments for the rapid, massively continuous heat treatment of metal parts of small or somewhat larger size. The cost of production of the furnace is diminished materially and assembly-wise by each and all of the above-emphasized improvements, without the slightest diminution of operational furnace efficiency and output.

What is claimed is:

1. A rotative barrel-type heat treating furnace, comprising a heating chamber having a retort journalled for rotation therein, said chamber and retort having means adjacent one axial end of the latter for both loading and unloading parts to be treated respectively into and out of a corresponding axial retort end, said retort being rotatively journalled by a retort trunnion part adjacent the opposite end thereof, and power transmitting parts disposed in the entirety thereof externally of said heating chamber for rotatively driving said retort.

2. A rotative barrel-type heat treating furnace comprising a heating chamber having a retort journalled for rotation therein, said chamber and retort having means adjacent one axial end of the latter for both loading and unloading parts to be treated respectively into and out of a corresponding axial retort end, said retort being rotatively journalled by a retort trunnion part adjacent the opposite axial end thereof, roller means coacting with said trunnion part for a stable rotative support of the retort in said heating chamber, and power transmitting parts disposed in the entirety thereof externally of said heating chamber for rotatively driving said retort.

3. A rotative barrel-type heat treating furnace, comprising a heating chamber having a retort journalled for rotation therein, and fluid pressure-powered means to tilt the chamber and its retort in a plane including the rotative axis of the retort, said chamber and retort having means adjacent one axial end of the latter for both loading and unloading parts to be treated respectively into and out of a corresponding axial retort end, said retort being rotatively journalled by a retort trunnion part adjacent the opposite axial end thereof, and power transmitting parts disposed in the entirety thereof externally of said heating chamber for rotatively driving said retort.

4. A rotative barrel-type heat treating furnace, comprising a heating chamber having a retort journalled for rotation therein, and fluid pressure-powered means to tilt the chamber and its retort in a plane including the rotative axis of the retort, said chamber and retort having means adjacent one axial end of the latter for both loading and unloading parts to be treated respectively into and out of a corresponding axial retort end, said retort being rotatively journalled by a retort trunnion parl adjacent the opposite axial end thereof, roller means coacting with said trunnion part for a stable rotative support of the retort in said heating chamber, and power transmitting parts disposed in the entirety thereof externally of said heating chamber for rotatively driving said retort.

5. The furnace of claim 1, in which said retort trunnion part receives means to introduce a treating medium through said part to the interior of the retort.

6. The furnace of claim 3, in which said retort trunnion part receives means to introduce a treating medium through said part to the interior of the retort.

7. The furnace of claim 4, in which said retort trunnion part receives means to introduce a treating medium through said part to the interior of the retort.

8. The furnace of claim 1, in which said heating chamber is journalled for pivotal movement about a transverse axis and has fluid pressure-operated means to tilt the chamber about said axis.

9. The furnace of claim 2, in which said heating chamber is journalled for pivotal movement about a transverse axis and has fluid pressure-powered means to tilt the chamber about said axis.

10. The furnace of claim 5, in which said heating chamber is journalled for pivotal movement about a transverse axis and has fluid pressure-powered means to tilt the chamber about said axis.

11. The furnace of claim 1, in which said heating chamber has further means at said one axial end thereof to introduce treating medium to the interior of the retort.

12. The furnace of claim 5, in which said heating chamber has further means at said one axial end thereof to introduce treating medium to the interior of the retort through a part of the loading means.

13. The furnace of claim 7, in which said heating chamber has further means at said one axial end thereof to introduce treating medium to the interior of the retort through a part of the loading means.

14. The furnace of claim 1, and further comprising heating means for the interior of said chamber.

15. The furnace of claim 14, in which said heating means comprises direct firing burners staggered longitudinally relative to one another on opposite sides of the axis of rotation of the retort, said burners discharging product of combustion into said chamber substantially tangentially of said retort.

16. The furnace of claim 14, in which said heating means comprises U-shaped heat transfer members disposed in said chamber parallel to the axis of said retort.

17. A rotative barrel-type heat treating furnace comprising a heating chamber having opposite end walls, a rotatable retort having a main cylindrical body portion within said heating chamber between said end walls and having a coaxial extension projecting through one of said end walls to the outside of said heating chamber,

rollers beneath'said cylindrical body portion for substantially the entire length for rotatably supporting said retort, first means outside of said heating chamber for rotating said rollers to thereby frictionally drive said retort in rotation and second means entirely outside of said heating chamber for rotating said projecting extension in timed relation to said rollers to thereby positively drive said retort in rotation.

18. A furnace according to claim 17 in which the end of said rotatable retort opposite said coaxial exten sion is entirely within the adjacent end Wall of said heating chamber and means is provided for both loading and unloading through said adjacent end wall into and out of said retort.

19. A furnace according to claim '18 in which treating gas is introduced into the retort through said coaxial extension and additional treating gas is introduced at the loading end.

References Cited UNITED STATES PATENTS 822,460 6/1906 Machlet 263--34 2,856,173 10/1958 Enk et al. 26334X 3,318,591 5/1967 Holcroft 263-34 3,386,719 6/1968 Martin 263-34 JOHN J. CAMBY, Primary Examiner 

